netdev - Re: [RFC PATCH 07/10] bnx2: remove skb_dma

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Date:	Mon, 30 Nov 2009 02:26:49 -0800
From:	"Michael Chan" <mchan@...adcom.com>
To:	"'Alexander Duyck'" <alexander.h.duyck@...el.com>,
	"Matthew Carlson" <mcarlson@...adcom.com>,
	"sathyap@...verengines.com" <sathyap@...verengines.com>,
	"subbus@...verengines.com" <subbus@...verengines.com>,
	"davem@...emloft.net" <davem@...emloft.net>
cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [RFC PATCH 07/10] bnx2: remove skb_dma_map/unmap calls from
 driver

Alexander Duyck wrote:

> Due to the fact that skb_dma_map/unmap do not work correctly when a HW
> IOMMU is enabled it has been recommended to go about removing
> the calls
> from the network device drivers.
>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>

Thanks Alexander.  Sorry for the late response, I just got back
from vacation.  It looks ok except in bnx2_free_tx_skbs():

> @@ -5295,18 +5303,30 @@ bnx2_free_tx_skbs(struct bnx2 *bp)
>               for (j = 0; j < TX_DESC_CNT; ) {
>                       struct sw_tx_bd *tx_buf = &txr->tx_buf_ring[j];
>                       struct sk_buff *skb = tx_buf->skb;
> +                     int k, last;
>
>                       if (skb == NULL) {
>                               j++;
>                               continue;
>                       }
>
> -                     skb_dma_unmap(&bp->pdev->dev, skb,
> DMA_TO_DEVICE);
> +                     pci_unmap_single(bp->pdev,
> +                                      pci_unmap_addr(tx_buf,
> mapping),
> +                                      skb_headlen(skb),
> +                                      PCI_DMA_TODEVICE);
>
>                       tx_buf->skb = NULL;
>
> -                     j += skb_shinfo(skb)->nr_frags + 1;
> +                     last = skb_shinfo(skb)->nr_frags;
> +                     for (k = 0; k < last; k++) {
> +                             tx_buf = &txr->tx_buf_ring[j + k + 1];

j + k + 1 can go beyond the ring when the ring wraps around.
I'll send an updated patch tomorrow.

> +                             pci_unmap_page(bp->pdev,
> +                                     pci_unmap_addr(tx_buf, mapping),
> +                                     skb_shinfo(skb)->frags[j].size,
> +                                     PCI_DMA_TODEVICE);
> +                     }
>                       dev_kfree_skb(skb);
> +                     j += k + 1;
>               }
>       }
>  }

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